Schottky barrier height is an important physical property of silicides as contacts to n-Si. Silicides having a high barrier height are known for semiconductor devices. However, there is need in bipolar semiconductor devices for low barrier silicide contacts. Transition metal silicides with a barrier lower than 0.5 eV have not been produced.
Silicides such as PtSi and IrSi have a barrier higher than 0.85 eV on n-Si and can be formed by reacting Pt or Ir on Si at 400.degree. for 30 minutes.
U.S. Pat. No. 3,349,297 discloses a semiconductor device wherein two metals having different barrier potential heights are employed in relation to a semiconductor material. In order to establish the available potential difference, it is necessary to have regions of both p-doped and n-doped silicon.
U.S. Pat. No. 3,968,272 discloses a method for creating low height for Schottky barriers. Schottky barriers that are between 0.15 eV and 0.20 eV are obtained by heat treatment of p-doped silicon on which palladium and platinum is deposited. If hafnium is placed onto n type silicon and heat treated at 400.degree..+-.25.degree. C., there is obtained a Schottky barrier of 0.15 eV.
U.S. Pat. No. 4,107,835 teaches the sharpening of the profile of a dopant beneath a metal silicide. The dopant is incorporated into the surface of a silicon substrate by ion implantation. Then, metal is deposited onto the surface and reacts with the silicon when heated. The dopant accumulates at the advancing surface of the metal silicide; and it may modify the Schottky barrier height slightly.